The present invention relates to an optoelectronic device and, more particularly, to an optoelectronic device having photocatalytic units.
Green plants, cyanobacteria and photosynthetic bacteria capture and utilize sunlight by means of reaction centers embedded in their membranes. In oxygenic plants and cyanobacteria, photon capture and conversion of light energy into chemical energy take place in specialized membranes called thylakoids. The thylakoids are located in chloroplasts in higher plants or consists of foldings of the cytoplasmic membrane in cyanobacteria. The thylakoids, consisting of stacked membrane disks (called grana) and unstacked membrane disks (called stroma). The thylakoid membrane contains two key photosynthetic components, photosystem I and photosystem II, designated PS I and PS II, respectively. Photosynthesis requires PSII and PSI working in sequence, using water as the source of electrons and CO2 as the terminal electron acceptor.
PS I is a transmembrane multisubunit protein-chlorophyll complex that mediates vectorial light-induced electron transfer from plastocyanin or cytochrome C553 to ferredoxin. The nano-size dimension, the energy yield of approximately 58% and the quantum efficiency of almost 1 makes the reaction center a promising unit for applications in molecular nano-electronics.
The crystalline structures of PS I in Synechococus elongatus and plant chloroplast have been resolved. In cyanobacteria, the complex consists of 12 polypeptides, some of which bind 96 light-harvesting chlorophyll and 22 carotenoid pigment molecules. The electron transport chain in PS I contains a special pair of chlorophyll (P700) that transfer electrons following photo excitation in 1 picoseconds (ps) to a monomeric chlorophyll a (Chl), through two intermediate phylloquinones (PQ) and three [4Fe-4S] iron sulfur centers (FeS), the final acceptors that are reduced in 0.2 □.
Attempts to attach plant PS I and bacterial reaction centers to metal surfaces are described in Lee, I., Stubna, A. & Greenbaum, E, “Measurement of electrostatic potentials above single photosynthetic reaction center,” J. Phys. Chem., B 104, 2439-2443 (2000); Das, R. et al., “Integration of photosynthetic protein molecular complexes in solid-state electronic devices,” Nano Letters 4, 1079-1083 (2004); Frolov, et al., “Fabrication of Photo-Electronic Device by Direct Chemical Binding of the Photosynthetic Reaction Center Protein to Metal Surfaces”, Adv. Mater. 17, 2434-2437 (2005); U.S. Patent Application No. 60/654,502 and International Patent Application No. IL2006/000241.